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libbpf: Split BTF presence checks into libbpf- and kernel-specific parts

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Needs for application BTF being present differs between user-space libbpf needs and kernel
needs. Currently, BTF is mandatory only in kernel only when BPF application is
using STRUCT_OPS. While libbpf itself relies more heavily on presense of BTF:
  - for BTF-defined maps;
  - for Kconfig externs;
  - for STRUCT_OPS as well.

Thus, checks for presence and validness of bpf_object's BPF needs to be
performed separately, which is patch does.

Fixes: 5327644614 ("libbpf: Relax check whether BTF is mandatory")
Reported-by: Michal Rostecki <mrostecki@opensuse.org>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Cc: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20200312185033.736911-1-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-03-12 11:50:33 -07:00 committed by Daniel Borkmann
parent 8d830f549d
commit b35f14f410
1 changed files with 12 additions and 5 deletions
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17
tools/lib/bpf/libbpf.c
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@ -2284,9 +2284,16 @@ static void bpf_object__sanitize_btf_ext(struct bpf_object *obj)
}
}
static bool bpf_object__is_btf_mandatory(const struct bpf_object *obj)
static bool libbpf_needs_btf(const struct bpf_object *obj)
{
return obj->efile.st_ops_shndx >= 0 || obj->nr_extern > 0;
return obj->efile.btf_maps_shndx >= 0 ||
obj->efile.st_ops_shndx >= 0 ||
obj->nr_extern > 0;
}
static bool kernel_needs_btf(const struct bpf_object *obj)
{
return obj->efile.st_ops_shndx >= 0;
}
static int bpf_object__init_btf(struct bpf_object *obj,
@ -2322,7 +2329,7 @@ static int bpf_object__init_btf(struct bpf_object *obj,
}
}
out:
if (err && bpf_object__is_btf_mandatory(obj)) {
if (err && libbpf_needs_btf(obj)) {
pr_warn("BTF is required, but is missing or corrupted.\n");
return err;
}
@ -2346,7 +2353,7 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
btf_ext__free(obj->btf_ext);
obj->btf_ext = NULL;
if (bpf_object__is_btf_mandatory(obj)) {
if (libbpf_needs_btf(obj)) {
pr_warn("BTF is required, but is missing or corrupted.\n");
return -ENOENT;
}
@ -2410,7 +2417,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
obj->btf_ext = NULL;
}
if (bpf_object__is_btf_mandatory(obj))
if (kernel_needs_btf(obj))
return err;
}
return 0;